This invention relates generally to a tape guiding assembly for a recording and/or reproducing apparatus, such as, a video tape recorder (VTR), and more particularly is directed to a tape guiding assembly, as aforesaid, which is included in a tape loading device by which tape is withdrawn from a cassette and wrapped helically about a circumferential surface of a guide drum provided with rotary heads for recording or reproducing signals in slant tracks scanned on the tape wrapped about the drum between a tape-entry position and a tape-exit position.
It has been proposed to provide a tape guiding assembly for a VTR which includes ultrasonically vibrated tape guides engageable by the tape adjacent the tape-entry and tape-exit positions, respectively, and auxiliary guide elements angled relative to the vibrated tape guides, respectively, and each being disposed for engagement by the tape between the respective vibrated tape guide and the tape-entry or tape-exit position, respectively. When such tape guiding assembly is included in a tape loading and unloading apparatus, the vibrated tape guides and the respective auxiliary guide elements are mounted on respective sliders which are movable between unloaded positions, in which the vibrated tape guides and auxiliary guide elements are engageable with the tape in a cassette, and loaded positions, in which the vibrated tape guides and respective auxiliary guide elements are disposed adjacent the tape-entry and tape-exit positions, respectively. When the sliders are moved from their unloaded positions to the respective loaded positions, the vibrated tape guides and auxiliary guide elements withdraw the tape from the cassette and wrap the tape about the circumferential surface of the guide drum between the tape-entry and tape-exit positions. When the vibrated tape guides are operated, ultrasonic vibrations are generated to reduce the frictional resistance to movement of the tape. Generally, the ultrasonically vibrated tape guides vibrate at frequencies between about 100 and 150 kHz with an amplitude of about 1 .mu.m.
In existing tape guiding assemblies employing ultrasonically vibrated tape guides, as aforesaid, the vibrations generated thereby are propagated past the adjacent relatively angled auxiliary guide elements to at least those portions of the tape wrapped about the guide drum which are adjacent the tape-entry and tape-exit positions. In the case of digital VTRs, the foregoing vibrations cause the error rate of the digital video signal to deteriorate to within a range of from 1.times.10.sup.-5 to 3.times.10.sup.-4 during recording or reproducing operations.
By reason of such deterioration of the error rate of the video signal during recording or reproducing operations, it is a disadvantage of existing tape guiding assemblies including ultrasonically vibrated tape guides that the latter are usually energized or operated only in the fast-forward or rewind mode. In other words, the ultrasonically vibrated tape guides are usually not vibrated in the recording or reproducing mode so that the reduction in the frictional resistance to movement of the tape is not then realized.
Further, in the known tape guiding assembly included in a tape loading and unloading apparatus, there is the danger that the tape, tape guides and the like will be damaged if the tape tension becomes excessive, for example, when the tape reaches one of the ends thereof in either the fast-forward mode or rewind mode without a sufficient deceleration theretofore.
Moreover, in previously proposed tape guiding assemblies included in tape loading and unloading apparatus and employing ultrasonically vibrated tape guides, the latter are mounted on respective sliders which, at the loaded positions, are located by respective stoppers disposed thereat. Contacts provided on each slider and on the respective stopper are mutually engaged with each other when the slider attains the loaded position so that power for energizing the respective vibrated tape guide can be supplied through the mutually engaged contacts. However, such contacts are engaged and disengaged at each loading and unloading operation and are either subject to relatively rapid wear or corrosion, or to the accumulation of foreign matter therebetween by which undesirably increased contact resistance and the unreliable transmission of power is experienced.
It is also to be noted that, in a previously proposed tape guiding assembly employing ultrasonically vibrated tape guides, each of the latter comprises a support shaft, a cylindrical metal bushing, usually of brass, slidable on the support shaft and having a plurality of annular bearing projections as integral parts of the bushing and being spaced apart in the axial direction on the outer surface of the bushing, a tubular tape guide, for example, of a ceramic, diametrically dimensioned to extend telescopically over the bushing and be supported, at the inner surface of the tubular tape guide, by the annular projections on the bushing, and an ultrasonic vibration generator fixed to the tubular tape guide at a side of the latter and being operative to generate an ultrasonic standing wave oscillation in the tubular tape guide with nodes thereof substantially at the annular projections. However, if the annular projections are not precisely located at vibration nodes, the tubular tape guide will move at its areas of contact with the annular projections and, by reason of the relatively hard material of such annular projections, will generate undesirable noise.